get full strength round up.. or generic [ a lot cheaper] .. none of that pre diluted stuff ...

put it in a container like at the link ...

cut to stump if planning on digging it out .... [cut flush to ground if not .. about a foot or two ... leaving NO LEAVES] ....

apply a line of RU around the edge of the cut ... it will get sucked into the cambian layer.. the vascular system of the plant.. and EVENTUALLY kill the plant ... 90% of the time... i use the applicator at the link

if anything sprouts up.. use hand shears and snip it off.. and put a drip of RU on it ...

i like to say.. pruning never killed anything.. and you are a prime example .... it takes a bit more than hope and prayer.. with most stuff ...

i said leave a foot or two ... so once its dead ... you can start digging it all out ... and often.. the leverage of the 2 feet.. allows you to move the stump around.. to find out where the next large roots is ...

a sawzall with a tree blade.. works wonders ... though it is tricky to use in soil ...

it once took me 3 years... to kill a very large underground poison ivy vine ... if you start in spring.. these should be dead by fall ... the point being.. just stay after them ...

i use a LOT of RU ... nothing ever died to root interaction ... simply a non-issue..IMHO

it is definitely NOT a diluted spray thing ...

ken

Here is a link that might be useful: link

Bigge, what type of tree is it? Root grafting with different species is somewhat unlikely.

its a fire brush tree about ten years old and ten foot tall, is it too late to dig up and transplant

Is a fire bush what we call a burning bush?

Either way I would think the difficulty would be WAY higher than it is worth. Let me tell you, one year I moved a six foot tall crepe myrtly. BIG mistake. Ended up involving my neighbor's truck lol. All for a plant I could have replaced for $20.

Burning bushes do